Enhanced field emission from ZnO nanowires grown on a silicon nanoporous pillar array

A large scale heterostructure array of ZnO nanowires/silicon nanoporous pillar array (Si-NPA) was prepared by a self-catalytic thermal evaporation and vapor-phase transport method, and an ultrahigh field emission current density of 1.55 mA cm−2 was obtained under an operating electric field of 4.0 V μm−1, with a low turn-on field of 1.65 V μm−1. The enhancement factor calculated according to the Fowler–Nordheim theory was ∼3141. The excellent field emission performance was attributed to the unique structure of ZnO/Si-NPA, especially the formation of ZnO nanowires on regular Si pillar array. Our work indicated that ZnO/Si-NPA might be an ideal candidate cathode of potential applications in flat panel displays and high brightness electron sources.